Coating composition, coating film, and laminated body

ABSTRACT

A coating composition that provides a coating film having better abrasion resistance. The composition includes: a fluororesin; and inorganic particles, the inorganic particles having a new Mohs hardness of 10 or higher and a substantially spherical shape. Also disclosed is a coating film produced from the coating composition and a laminate such as a cooking utensil including a substrate and the coating film.

TECHNICAL FIELD

The present invention relates to a coating composition, a coating film,and a laminate. More specifically, the present invention relates to acoating composition and a coating film each containing a fluororesin andinorganic particles, and a laminate including the coating film.

BACKGROUND ART

Cooking utensils (e.g., frying pans, electric griddles, pots, and innerpots of rice cookers) are commonly provided with a coating layer of afluororesin excellent in properties such as heat resistance,non-adhesiveness, and stain resistance, on a metal substrate ofaluminum, stainless steel, or the like for the purpose of preventingscorching or sticking of cooking ingredients during cooking with heat.

In production of such cooking utensils having a coating layer of afluororesin, various inorganic materials are often added, as filler, tomaterials for forming a coating layer with an aim of mainly improvingthe abrasion resistance.

For example, Patent Literature 1 discloses a heat cooker in which asingle layer of a non-sticky coating formed of a spherical ceramicpigment, potassium hexatitanate whisker, and a fluororesin coatingcomposition is formed on a cooking surface made of aluminum or analuminum alloy.

Patent Literature 2 discloses that, for the purpose of further improvingthe hardness and abrasion resistance properties of a fluorinatedcoating, an anti-corrosive coating composition may contain hard fillerparticles of any of aluminum oxide, silicon carbide, zirconium oxide,and a scrap metal such as aluminum scrap, zinc scrap, and silver scrap.

CITATION LIST Patent Literature

Patent Literature 1: JP H10-323283 A

Patent Literature 2: JP 2013-506739 T

SUMMARY OF INVENTION Technical Problem

The present invention aims to provide a coating composition that gives acoating film with better abrasion. resistance, and a coating film withbetter abrasion resistance.

Solution to Problem

The present inventors made an intensive study to find out that the useof particles having a new Mohs hardness of 10 or higher and having asubstantially spherical shape as inorganic particles can surprisinglyimprove the abrasion resistance of coating films, thereby completing thepresent invention. Conventional coating compositions and coating filmshave contained inorganic particles prepared only by pulverizing.However, the inorganic particles prepared only by pulverizing cannotsufficiently improve the abrasion resistance of coating films.

Specifically the present invention relates to a coating compositionincluding: a fluororesin; and inorganic particles, the inorganicparticles having a new Mohs hardness of 10 or higher and having asubstantially spherical shape.

In the coating composition, the inorganic particles viewed from anarbitrary angle preferably have an average circularity of 0.90 to 1.00.

In the coating composition, the inorganic particles are preferably atleast one kind selected from the group consisting of alumina particlesand silicon carbide particles.

In the coating composition, the fluororesin is preferablypolytetrafluoroethylene.

In the coating composition, the fluororesin contained preferablyincludes polytetrafluoroethylene alone or, polytetrafluoroethylene and afluororesin other than polytetrafluoroethylene, and the amount of thepolytetrafluoroethylene is preferably 20% by mass or more relative tothe total amount of the polytetrafluoroethylene and the fluororesinother than polytetrafluoroethylene.

In the coating composition, the amount of the inorganic particles ispreferably 1 to 40% by mass relative to the amount of the fluororesin.

The present invention also relates to a coating film produced from thecoating composition described above.

The present invention also relates to a coating film including: afluororesin; and inorganic particles, the inorganic particles having anew Mohs hardness of 10 or higher and having a substantially sphericalshape.

In the coating film, the inorganic particles viewed from an arbitraryangle preferably have an average circularity of 0.90 to 1.00.

In the coating film, the inorganic particles are preferably at least onekind selected from the group consisting of alumina particles and siliconcarbide particles.

In the coating film, the fluororesin is preferablypolytetrafluoroethylene.

In the coating film, the fluororesin contained preferably includespolytetrafluoroethylene alone or polytetrafluoroethylene and afluororesin other than polytetrafluoroethylene, and the amount of thepolytetrafluoroethylene is preferably 20% by mass or more relative tothe total amount of the polytetrafluoroethylene and the fluororesinother than polytetrafluoroethylene.

In the coating film, the amount of the inorganic particles is preferably1 to 40% by mass relative to the amount of the fluororesin.

The present invention also relates to a laminate including: a substrate;and a coating film produced from the coating composition described aboveor the coating film described above.

The laminate may be a cooking utensil.

Advantageous Effects of Invention

Having the above constitution, the coating composition of the presentinvention can provide a coating film with excellent abrasion resistance.

Having the above constitution, the coating film of the present inventionhas excellent abrasion resistance.

A coating film prepared from the coating composition of the presentinvention and the coating film of the present invention can beparticularly suitably used as a top coat layer covering the surface of acooking utensil.

The laminate and cooking utensil of the present invention each haveexcellent abrasion resistance.

DESCRIPTION OF EMBODIMENTS

The present invention is specifically described in the following.

The coating composition of the present invention contains a fluororesinand inorganic particles.

The fluororesin is preferably at least one selected from the groupconsisting of polytetrafluoroethylene (PTFE), tetrafluoroethylene(TFE)/perfluoro(alkyl vinyl ether) (PAVE) copolymers (PFA),TFE/hexafluoropropylene (HFP) copolymers (FEP), ethylene (Et)/TFEcopolymers (ETFE), Et/TFE/HFP copolymers, polychlorotrifluoroethylene(PCTFE), chlorotrifluoroethylene (CTFE)/TFE copolymers, Et/CTFEcopolymers, and polyvinylidene fluoride (PVDF), more preferably at leastone selected from the group consisting of PTFE, PFA, and FEP.

In particular, the fluororesin is preferably PTFE because the formedcoating film has particularly excellent abrasion resistance.

The PTFE preferably has fibrillation properties. In the case where thePTFE has fibrillation properties, the inorganic particles are not likelyto fall off the coating film, leading to further better abrasionresistance of the coating film.

The presence of the fibrillation properties can be confirmed by “pasteextrusion”, a typical method of molding “high-molecular-weight PTFEpowder” that is a powder prepared from a polymer of TEE, because thefibrillation properties of the high-molecular-weight PTFE enables pasteextrusion thereof. In the case where an unfired molded product obtainedby the paste extrusion has substantially no strength or elongation, forexample, in the case where the molded product has an elongation of 0%and is broken when pulled, the molded product is considered to have nofibrillation properties.

The PTFE preferably has non-melt-fabricability. Thenon-melt-fabricability refers to a property that the melt flow ratecannot be measured in conformity with ASTM D-1238 and D-2116 at atemperature higher than the crystallization melting point.

For further better abrasion resistance, the PTFE has a standard specificgravity (SSG) of preferably 2.13 to 2.23, more preferably 2.13 to 2.19.The SSG is the SSG determined in ASTM 04895-89 as the index of themolecular weight of polytetrafluoroethylene having no melt-moldingfabricability.

The PTFE preferably has a melting point of 325° C. to 347° C. Themelting point is a value measured by differential scanning calorimetry(DSC) at a rate of temperature rise of 10° C./min.

The PTFE may be either a TFE homopolymer consisting oftetrafluoroethylene (TFE) alone or modified PTFE including TFE and amodifying monomer. The modifying monomer is not particularly limited aslong as it is copolymerizable with TFE. Examples thereof include:perfluoroolefins such as hexafluoropropylene (HFP); chlorofluoroolefinssuch as chlorotrifluoroethylene (CTFE); hydrogen-containingfluoroolefins such as trifluoroethylene and vinylidene fluoride (VDF);perfluorovinyl ethers; perfluoroalkyl ethylenes; and ethylene. A singlemodifying monomer or multiple modifying monomers may be used.

The perfluorovinyl ethers are not particularly limited, and examplesthereof include an unsaturated perfluoro compound represented by theformula (1):

CF₂═CF—ORf   (1),

where Rf represents a perfluoro organic group. The “perfluoro organicgroup” as used herein refers to an organic group in which all thehydrogen atoms bonded to carbon atoms are substituted with fluorineatoms. The perfluoro organic group may have ether oxygen.

Examples of the perfluorovinyl ethers include perfluoro (alkyl vinylether) (PAVE) which is a compound represented by the formula (1) whereRf is a C1-C10 perfluoroalkyl group. The carbon number of theperfluoroalkyl group is preferably 1 to 5.

Examples of the perfluoroalkyl group in the PAVE include aperfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group,a perfluorobutyl group, a perfluoropentyl group, and a perfluorohexylgroup. Preferred is a perfluoro(propyl vinyl ether) (PPVE) in which theperfluoroalkyl group is a perfluoropropyl group.

Examples of the perfluorovinyl ethers further include a compoundrepresented by the formula (I) where Rf is a C4-C9perfluoro(alkoxyalkyl) group, a compound represented by the formula (1)where Rf is a group represented by the following formula:

where m is an integer of 0 or 1 to 4, and a compound represented by theformula (1) where Rf is a group represented by the following formula:

where n is an integer of 1 to 4.

The perfluoroalkyl ethylenes are not particularly limited, and examplesthereof include (perfluorobutyl) ethylene (PFBE) and(perfluorohexyl)ethylene.

The modifying monomer of the modified PTFE is preferably at least oneselected from the group consisting of HFP, CTFE, VDF, PPVE, PFBE, andethylene. The modifying monomer is more preferably at least one selectedfrom the group consisting of HFP and CTFE.

In the modified PTFE, the amount of the modifying monomer unit ispreferably 1% by mass or less, more preferably 0.001 to 1% by mass,based on the total amount of all monomer units. The modifying monomerunit as used herein means a part derived from a modifying monomer in themolecular structure of the modified PTFE. The term “all monomer units”means all parts derived from monomers in the molecular structure of themodified PTFE.

From the standpoint of non-adhesiveness, the coating compositionpreferably contains the fluororesin in an amount of 30.0 to 99.0% bymass. The amount of the fluororesin is more preferably 40.0% by mass ormore and 97.0% by mass or less.

The coating composition may contain the PTFE and a fluororesin otherthan the PTFE. Examples of the fluororesin other than the PTFE includeTFE/PAVE copolymers (PFA), TFE/HFP copolymers (FEP), ethylene (Et)/TFEcopolymers (ETFE), Et/TFE/HFP copolymers, polychlorotrifluoroethylene(PCTFE), CTFE/TFE copolymers, Et/CTFE copolymers, and polyvinylidenefluoride (PVDF).

The fluororesin other than the PTFE is preferably melt-fabricable. Theterm “melt-fabricable” means that the polymer can be molten andfabricated using a conventional fabrication device such as an extruderor an injection molding apparatus. The fluororesin therefore commonlyhas a melt flow rate (MFR) of 0.01 to 100 g/10 min.

The MFR is a value obtained as the mass (g/10 min) of the polymer flownfrom a nozzle (inner diameter: 2 mm, length: 8 mm) per 10 minutesmeasured in conformity with ASTM D1238 using a melt indexer (YasudaSeiki Seisakusho Ltd.) at a measuring temperature (e.g., 372° C. for PFAand FEP, 297° C. for ETFE) and a load (e.g., 5 kg for PFA, FEP, andETFE) each determined in accordance with the kind of the fluororesin.

The fluororesin other than the PTFE has a melting point of preferably150° C. or higher and lower than 322° C., more preferably 200° C. to320° C., still more preferably 240° C. to 320° C. The melting point is atemperature corresponding to the maximum value of a heat-of-fusion curveobtained by increasing the temperature using a differential scanningcalorimeter (DSC) at a rate of 10° C./rain.

The coating composition preferably contains, as the fluororesin, theFIFE alone or the PTFE and a fluororesin other than the PTFE.

In the coating composition, the amount of the PTFE is preferably 1% bymass or more, more preferably 20% by mass or more, still more preferably10% by mass or more, particularly preferably 70% or more, relative tothe total amount of the PTFE and the fluororesin other than the PTFE.The upper limit of the amount may be 100% by mass.

In the case where the coating composition contains the PTFE and afluororesin other than the PTFE, the mass ratio between the PTFE and thefluororesin other than the PTFE is preferably 1/99 to 99/1, morepreferably 10/90 to 99/1, still more preferably 20/80 to 99/1. If theamount of the PTFE is too small, the abrasion resistance of the coatingfilm may be insufficient.

The mass of the FIFE contained in the coating composition can becalculated by a known analysis method such as infrared spectroscopy orthermogravimetry-differential thermal analysis (TG-DTA).

The coating composition may contain a heat-resistant resin. Theheat-resistant resin generally has only to be a resin that is recognizedto have heat resistance, and is preferably a resin having a continuousservice temperature of 150° C. or higher. It should be noted that theheat-resistant resin does not include the above fluororesin.

The heat-resistant resin is not particularly limited, and is preferablyat least one resin selected from the group consisting of polyamide imideresins, polyimide resins, polyether sulfone resins, polyetherimideresins, polyether ether ketone resins, aromatic polyester resins, andpolyarylene sulfide resins.

The polyamide imide resins (PAI) are resins each formed of a polymerhaving an amide bond and an imide bond in the molecular structure. ThePAI is not particularly limited, and examples thereof include resinsformed of any high molecular weight polymer obtained by any of thefollowing reactions: a reaction between an aromatic diamine having anamide bond in the molecule and an aromatic tetravalent carboxylic acid(e.g., pyromellitic acid); a reaction between an aromatic trivalentcarboxylic acid (e.g., trimellitic anhydride) and a diamine (e.g.,4,4-diaminophenyl ether) or a diisocyanate (e.g., diphenylmethanediisocyanate); and a reaction between a dibasic acid having an aromaticimide ring in the molecule and a diamine. For excellent heat resistance,the PAI is preferably a resin formed of a polymer having an aromaticring in the main chain.

The polyimide resins (PI) are resins each formed of a polymer having animide bond in the molecular structure. The PI is not particularlylimited, and examples thereof include resins formed of any highmolecular weight polymer obtained by a reaction of an aromatictetravalent carboxylic anhydride such as pyromellitic anhydride. Forexcellent heat resistance, the PT is preferably a resin formed of apolymer having an aromatic ring in the main chain.

The polyether sulfone resins (PES) are resins each formed of a polymerhaving a repeating unit represented by the following formula.

The PES is not particularly limited, and examples thereof include resinsformed of any polymer obtained by polycondensation of dichlorodiphenylsulfoneand bisphenol.

In order to achieve excellent adhesion to the substrate, to achievesufficient heat resistance even, at temperature for sintering performedin forming cooking utensils, and to achieve excellent corrosionresistance of the resulting cooking utensils, the heat-resistant resinis preferably at least one resin. selected from the group consisting ofPIAs, PIs, and PESs. PAIs, PIs, and PESs may be used alone or may beused in combination of two or more in each group.

For excellent adhesion to the substrate and heat resistance, theheat-resistant resin is more preferably at least one resin selected fromthe group consisting of PAIs and PIs.

For excellent corrosion resistance, the heat-resistant resin ispreferably a mixture of a PES and at least one selected from the groupconsisting of PAIs and PIs. In other words, the heat-resistant resin maybe a mixture of a PES and a PAI, a mixture of a PES and a PI, or amixture of a PES, a PAI, and a PI. The heat-resistant resin isparticularly preferably a mixture of a PES and a PAI.

The coating composition contains inorganic particles having asubstantially spherical shape. Containing inorganic particles having asubstantially spherical shape, the coating composition can give acoating film with excellent abrasion resistance. The inorganic particlesdo not contain inorganic particles prepared only by pulverizing butcontain inorganic particles prepared by pulverizing and subsequentspheroidization.

From the standpoint of abrasion resistance, the inorganic particles arepreferably particles having substantially no angularity. The inorganicparticles preferably have a shape of a sphere, an elliptical sphere, arounded polyhedron, or a polyhedron with a circularity value close to 1.

From the standpoint of abrasion resistance, the inorganic particles hasa new Mohs hardness of 10 or higher, preferably 12 or higher. Thehardness of glass beads or silica having a new Mohs hardness of 7 is toolow, and therefore, the use thereof as the inorganic particles cannotprovide a coating film with excellent abrasion resistance. Examples ofthe inorganic particles having a new Mohs hardness of 10 or higherinclude particles of diamond, fluorinated diamond, boron carbide,silicon carbide, aluminum oxide (including ruby and sapphire),chrysoberyl, garnet, and fused zirconia.

The inorganic particles have an average particle size of preferably 5 to40 μm, more preferably 10 μm or more. In the case of using the inorganicparticles for forming a coating film with a thickness of 20 μm or less,the average particle size is more preferably 30 μm or less from thestandpoint of surface smoothness.

The average particle size can be determined, for example, with a laserdiffraction scattering particle size analyzer available from NikkisoCo., Ltd.

The inorganic particles viewed from an arbitrary angle preferably havean average circularity of 0.90 or higher. The average circularity ismore preferably 0.91 or higher, still more preferably 0.93 or higher,particularly preferably 0.95 or higher, and preferably 1.00 or lower.

The inorganic particles include a particle mixture having an averagecircularity of 0.90 or higher (or within the preferable neumericalrange) obtained by uniformly mixing inorganic particles having a newMohs hardness of 10 or higher and an average circularity of 0.90 orhigher and particles having a new Mohs hardness of 10 or higher and anaverage circularity of less than 0.90.

The average circularity can be determined by an image processing programusing a flow particle image analyzer.

From the standpoint of abrasion resistance, the inorganic particles arepreferably at least one type selected from the group consisting ofalumina particles and silicon carbide particles. The inorganic particlesare preferably silicon carbide particles because the obtained coatingfilm has still higher abrasion resistance.

The alumina may be either amorphous or crystalline, and may be, forexample, a crystalline alumina such as γ-alumina having a γ phase as theprincipal crystal phase or α-alumina having an α phase as the principalcrystal phase.

The alumina particles having a substantially spherical shape can beprepared by a known method such as spraying spheroidization.

The alumina particles can be also produced by the following methods.

To an aqueous solution in which a carboxylic acid compound is dispersedor dissolved are added an aqueous solution and an aqueous solution of aneutralizer at the same time, thereby forming particles of a hydroxideor hydrate of the metal, and the obtained particles are fired (see JPH05-139704 A, for example).

Aluminum alkoxide is brought into contact with water in the presence ofan alcohol and a bipolar nonprotonic solvent to be hydrolized, withoutforming an emulsion, to prepare aluminum hydroxide, and the aluminumhydroxide is fired (see JP H08-198622 A, for example).

A flammable liquid containing an aluminum-containing compound is sprayedinto droplets, and burned so that the aluminum-containing compound isconverted to alumina and spheroidized (see JP H11-147711 A, forexample).

Aluminum hydroxide with a dehydration temperature of 450° C. or higherand a purity of 99.9% by mass or higher is fired within a temperaturerange of 800° C. or higher and 1200° C. or lower in a chlorineatmosphere to give α-alumina particles (see JP 2001-302236 A, forexample).

A small amount of an agent conventionally known as a mineralizer or acrystal growth accelerator for alumina, such as a halogen compound and aboron compound, is added to a pulverized product of fused alumina orsintered alumina and heating treatment is performed at a temperature of1000° C. to 1550° C. (see JP-A H05-294613, for example).

Aluminum hydroxide powder or a slurry thereof is sprayed to a flame, andthe obtained powder is collected at a high temperature of 500° C. orhigher (see JP 2001-19425 A and JP 2001-226117 A, for example).

Powder of alumina or aluminum hydroxide is passed through ahigh-temperature region at 2000° C. or higher for a distance of 10 cm orlonger to be formed into fused droplets, and the fused droplets arefallen to be cooled and solidified in a spherical shape by a free fallmethod (see JP 2005-179109 A, for example).

The silicon carbide particles having a substantially spherical shape canbe prepared by a known method such as spraying spherocrystalization.

Alternatively, the silicon carbide particles can be prepared by a methodincluding the step of preparing porous spherical particles byspray-drying a slurry of raw material silicon carbide that is an α-typecrystal with an average particle size of 1 μm or less, and sintering theobtained porous spherical particles (see JP 2013-095637 A, for example).

In terms of abrasion resistance, the coating composition preferablycontains the inorganic particles in an amount of 1 to 40% by massrelative to the amount of the fluororesin. The amount of the inorganicparticles is more preferably 3% by mass or more and 30% by mass or less.

The coating composition contains the inorganic particles having a newMohs hardness of 10 or higher and having a substantially sphericalshape. The coating composition may further contain inorganic particleshaving a new Mohs hardness of lower than 10. Since the inorganicparticles having a new Mohs hardness of lower than 10 do not affect theabrasion resistance, the shape thereof may be either substantiallyspherical or not spherical.

Examples of the inorganic particles having a new Mohs hardness of lowerthan 10 include colorants (e.g., glass, mica, carbon black, clay, talc,tourmaline, jade, germanium, barium sulfate, calcium carbonate, silicastone, topaz, beryl, quartz, titanium oxide, and iron oxide) andpotassium titanate.

The coating composition may be either liquid or powder, and ispreferably liquid. In the case where the coating composition is liquid,a flat and smooth coating fills can be obtained. Moreover, in thesurface of the coating film, the inorganic particles are uniformlydispersed to exert the expected effect of abrasion resistance.

The coating composition may contain a liquid medium such as water and/oran organic liquid, and preferably contains water. In such a case, thecoating composition may have a solid content concentration of 10 to 80%by mass. The “organic liquid” refers to an organic compound that isliquid at a normal temperature at around 20° C.

For formation of a further flat and smooth coating film, the coatingcomposition also preferably contains a surfactant. The surfactant may bea conventionally known surfactant.

The coating composition can be prepared by a conventional mixing methodsuch as a method of mixing the fluororesin, the inorganic particles, andthe like using a mixer or a roll mill.

The coating composition may further contain any additive. The additiveis not particularly limited, and examples thereof include levelingagents, solid lubricants, precipitation inhibitors, moisture absorbents,surface conditioners, thixotropic agents, viscosity modifiers,anti-gelling agents, ultraviolet absorbers, photostabilizers,plasticizers, anti-flooding agents, anti-skinning agents, scratchinhibitors, fungicides, antibiotics, antioxidants, antistatics,silane-coupling agents, colorants (e.g., carbon black, clay, talc,tourmaline, jade, germanium, extender pigments, silica. stone, topaz,beryl, quartz, scaly pigments, glass, mica, titanium oxide, and ironoxide), film-forming agents (e.g., acrylic resins, urethane resins,polyethylene glycol, and polypropylene glycol), various reinforcingmaterials, various fillers, conductive fillers, and metal powders ofgold, silver, copper, platinum, or stainless steel.

The coating composition is applied to a substrate to form a coatingfilm. The coating film of the coating composition may be either atop-coat coating film or a primer coating film. Alternatively, thecoating film may constitute an intermediate layer. The formed coatingfilm is excellent in abrasion resistance. The present invention alsoencompasses a coating film prepared using the coating composition.

The coating composition may be applied to a substrate by any method. Forthe liquid coating composition, examples of the method include spraycoating, roll coating, doctor blade coating, dip (immersion) coating,impregnation coating, spin-flow coating, and curtain-flow coating.Preferred is spray coating. For the powder coating composition, examplesof the method include electrostatic coating, fluidized dip coating, androtolining. Preferred is electrostatic coating.

After application of the coating composition, the coating film is fired.The firing is preferably performed after drying. The drying ispreferably performed at a temperature of 80° C. to 200° C. for 5 to 30minutes. The firing is preferably performed at a temperature of 300° C.to 400° C. for 10 to 90 minutes.

The present invention also encompasses a coating film containing thefluororesin and inorganic particles that have a new Mobs hardness of 10or higher and has a substantially spherical shape. The coating film maybe either a top-coat coating film or a primer coating film.Alternatively, the coating film may constitute an intermediate layer.The coating film of the present invention can be produced from thecoating composition of the present invention.

In the coating film, the amount of the fluororesin is preferably 60 to99% by mass relative to the total mass of the coating film. The amountof the fluororesin is more preferably 70% by mass or more and 97% bymass or less.

Examples of the fluororesin and the inorganic particles are the same asthose exemplified as components of the coating composition of thepresent invention. The preferable amounts thereof are also the same asthose of the coating composition of the present invention.

Specifically, the coating film preferably contains, as the fluororesin,the PTFE alone or a combination of the PTFE and a fluororesin other thanthe PTFE.

In the coating film, the amount of the PTFE is preferably 1% by mass ormore, more preferably 20% by mass or more, still more preferably 40% bymass or more, particularly preferably 70% or more, relative to the totalamount of the PTFE and the fluororesin other than the PTFE. The upperlimit of the amount may be 100% by mass.

In the case where the coating film contains the PTFE and a fluororesinother than the PTFE, the mass ratio of the PTFE and the fluororesinother than the PTFE is preferably 1/99 to 99/1, more preferably 10/90 to99/1, still more preferably 20/80 to 99/1. If the amount of the PTFE istoo small, the abrasion resistance of the coating film may beinsufficient.

In the coating film, the amount of the inorganic particles is preferably1 to 40% by mass relative to the amount of the fluororesin. The amountof the inorganic particles is more preferably 3% by mass or more and 30%by mass or less.

The coating film preferably has a thickness of 1 to 100 μm. Thethickness is more preferably 10 μm or more and 50 μm or less.

The coating film may contain those exemplified as optional componentsfor the coating composition of the present invention, such as inorganicparticles having a new Mohs hardness of less than 10, a heat-resistantresin, a surfactant, and additives.

Whether or not the inorganic particles contained in the coating filmcorresponds to the inorganic particles having a new Mohs hardness of orhigher can be determined by heating the coating film to a temperaturenot lower than the temperature at which organic components such as thefluororesin are burned off and then specifying the material of inorganicresidues resulting from the heating by a known analysis method such asscanning electron microscopy/energy dispersive X-ray spectroscopy(SEM-EDX), X-ray photoelectron spectroscopy (XPS), or time-of-flightsecondary ion mass spectrometry (TOF-SIMS).

The average circularity of the inorganic particles having a new Mohshardness of 10 or higher contained in the coating film can be determinedby heating the coating film to a temperature not lower than thetemperature at which organic components such as the fluororesin areburned off, subjecting the inorganic residues resulting from the heatingto elemental mapping by SEM-EDX to specify a part corresponding to theparticles having a new Mohs hardness of 10 or higher, and analyzing theparticle in this image with an image analysis program such as Mac-Viewavailable from Mountech Co., Ltd.

The mass of the PTFE contained in the coating film, relative to thetotal mass of the PTFE and the fluororesin other than the PTFE can becalculated by a known method such as infrared spectroscopy or TG-DTA.

The amount of the inorganic particles having a new Mohs hardness of 10or higher contained in the coating film, relative to the amount of thefluororesin, can be calculated by combining known techniques such asTG-DTA, elemental analysis, and elemental mapping.

The present invention also encompasses a laminate including the coatingfilm.

Characters or drawings may be printed on the coating film. The printingmethod is not particularly limited, and examples thereof include padprinting. A printing ink used for the printing is not particularlylimited, and examples thereof include a composition containing PES, aTFE homopolymer, and titanium oxide.

The laminate preferably further includes a substrate. The coating filmmay be either directly provided on the substrate or provided on thesubstrate via another layer. Moreover, still another layer may beprovided on the coating film.

The laminate also preferably includes two or more layers of the coatingfilms. Two or more layers of the coating films can contribute not onlyto further improvement of the abrasion resistance but also to, forexample, improvement of the surface smoothness, design, and corrosionresistance.

The laminate also preferably includes another layer other than thesubstrate and the coating film. Examples of such a layer include aprimer layer and an intermediate layer. These layers are commonlyprovided between the substrate and the coating film.

The laminate is more preferably: a laminate including a substrate andthe coating film formed on the substrate; a laminate including asubstrate, a primer layer formed on the substrate, and the coating filmformed on the primer layer; or a laminate including a substrate, aprimer layer formed on the substrate, an intermediate layer formed onthe primer layer, and the coating film formed on the intermediate layer.Two or more intermediate layers may be provided.

The laminate may include a layer formed on the coating film for thepurpose of achieving the effects of improving the surface smoothness,design, non-adhesiveness, and corrosion resistance. However, since thecoating film has excellent abrasion resistance, no layer is preferablyformed on the coating film. In other words, the coating film ispreferably used as a top coat. The laminate preferably includes thecoating film as a top coat.

The substrate may be formed of any material, and examples of thematerial include metals such as simple metals (e.g., iron, aluminum,stainless steel, and copper) and alloys thereof; and non-metallicinorganic materials such as enamel, glass, and ceramic. Examples of thealloys include stainless steel.

The substrate may be subjected to any surface treatment before the use,such as degreasing treatment or surface-roughening treatment, ifnecessary. The surface-roughening treatment may be performed by anymethod, and examples thereof include chemical etching with acid oralkali, anodizing (formation of anodic oxide coating), and sandblasting.In order to uniformly apply a primer composition for forming the primerlayer without cissing, and to improve the adhesion between the substrateand the primer layer, the surface treatment may be appropriately chosenin accordance with the kinds of the substrate and the primercomposition, and at is preferably sandblasting, for example.

The substrate may be subjected to a degreasing treatment in which thesubstrate is heated at 380° C. so that impurities such as oil arepyrolized and removed before the use. For better adhesion between thesubstrate and the coating film, an aluminum substrate which has beensubjected to a surface-roughening treatment with an alumina abrasiveafter the surface treatment is preferably used.

The primer layer preferably contains a heat-resistant resin. Examples ofthe preferred heat-resistant resin are the same as those exemplified asthe heat-resistant resin contained in the coating composition.

The amount of the heat-resistant resin is preferably 10 to 50% by massof the primer layer, more preferably 15% by mass or more and 40% by massor less, still more preferably 30% by mass or less.

The primer layer may or may not further contain a fluororesin. Examplesof the fluororesin include PTFE, polychlorotrifluoroethylene (PCTFE),polyvinylidene fluoride (PVdF), polyvinyl fluoride (PVF), TFE/PAVEcopolymers (PFA), TFE/HFP copolymers (FEP), TFE/CTFE copolymers, TFE/VdFcopolymers, TFE/3FH copolymers, Et/TFE copolymers (ETFE), TFE/Prcopolymers, VdF/HFP copolymers, Et/CTFE copolymers (ECTFE), and Et/HFPcopolymers. In particular, the primer layer preferably contains at leastone selected from the group consisting of PTFE, PFA, and FEP.

The amount of the fluororesin is preferably 90 to 0% by mass of theprimer layer, more preferably 85% by mass or less of the primer layer.

The primer layer may further contain inorganic particles. The inorganicparticles are not particularly limited, and examples thereof includeinorganic nitrides, carbides, borides, and oxides of zirconium,tantalum, titanium, tungsten, silicon, aluminum, or beryllium; anddiamond, silicon carbide, and aluminum oxide. The inorganic particlesmay have a shape of, but not limited to, particles, flakes, or the like.

The primer layer may contain additives) in addition to the fluororesin,the heat-resistant resin, and the inorganic particles. Any additive maybe contained, and examples thereof include those exemplified for thecoating composition.

The primer layer has a thickness of preferably 1 to 40 μm, morepreferably 5 to 35 μm. Too thin a primer layer may not be expected toshow an anchor effect and may easily cause pinholes, so that thecorrosion resistance of the laminate may be poor. Too thick a primerlayer may easily suffer film defects such as cracks or scabs, so thatthe abrasion resistance, hardness, and corrosion resistance of thelaminate may be poor. The upper limit of the thickness of the primerlayer is still more preferably 30 μm, particularly preferably 25 μm.

The intermediate layer preferably contains a fluororesin. The preferablefluororesin is the same as that contained in the primer layer.

The amount of the fluororesin is preferably 60 to 100% by mass relativeto the total mass of the intermediate layer. The amount of thefluororesin is more preferably 65 to 100% by mass, still more preferably70 to 100% by mass. The use of the fluororesin within the above rangecan improve the adhesion between the intermediate layer and the coatingfilm adjacent to the intermediate layer.

In the case where the intermediate layer is formed of the fluororesinand the heat-resistant resin, the intermediate layer has excellentadhesion to the primer layer because the heat-resistant resin in theintermediate layer has an affinity to the heat-resistant resin in theprimer layer. The intermediate layer also has excellent adhesion to thecoating film because the fluororesin in the intermediate layer has anaffinity to the fluororesin in the coating film. As above, in the casewhere the intermediate layer is formed of the fluororesin and theheat-resistant resin, the intermediate layer has excellent adhesion toboth the primer layer and the coating film.

The intermediate layer may further contain inorganic particles. Theinorganic particles are preferably particles of at least one selectedfrom the group consisting of inorganic nitrides, carbides, borides, andoxides of zirconium, tantalum, titanium, tungsten, silicon, aluminum, orberyllium; and diamond. In terms of easy availability and cost,preferred is silicon carbide or aluminum oxide. The inorganic particlesmay have a shape of, but not limited to, particles, flakes, or the like.

The amount of the inorganic particles is preferably 0.1 to 30% by mass,more preferably 1% by mass or more and 20% by mass or less of theintermediate layer.

The intermediate layer may contain additive(s) in addition to thefluororesin, the heat-resistant resin, and the inorganic particles. Anyadditive may be contained, and examples thereof include thoseexemplified for the coating composition.

The intermediate layer can be formed, for example, by applying acomposition for an intermediate layer containing the fluororesin and theheat-resistant resin to a primer layer, and optionally drying and thenfiring the applied composition.

The intermediate layer has a thickness of preferably 5 to 30 μm, morepreferably 10 to 25 μm.

The laminate can be suitably used for cooking utensils or industrialcomponents for machineries or automobiles. The present invention alsoencompasses the cooing utensils. The cooking utensils and the industrialcomponents for machineries or automobiles can maintain sufficientabrasion resistance even after use under a high temperature environmentsuch as cooking with heat.

Examples of the cooking utensils include frying pans, pressure cookers,pots, electric skillets, rice cookers, ovens, electric griddles, breadbaking pans, knives, gas cooktops, bread makers, inner surfaces ofmicrowave ovens, hot water dispensers, electric kettles, Taiyaki(Japanese fish-shaped cake) makers, waffle makers, and hot sandwichmakers. Examples of the industrial components for machineries orautomobiles include engine pistons, stabilizers, reed valve sheets,wires, and bearings for automobiles.

EXAMPLES

The present invention is specifically described in the following withreference to, but not limited to, examples.

The numerical values in the examples were determined by the followingmethods.

Measurement of Average Circularity

The value measured with FPIA-2100 available from. Sysmex Corporation wastaken as the average circularity.

The numerical value data provided by the raw material maker measured forabout 10,000 particles (effectively analyzed particles) in a test sampleprepared by mixing 1.5 g of the particles with 30 ml of an appropriatesolvent such as sodium hexametaphosphate, with a flow particle imageanalyzer FPIA-2100 available from Sysmex Corporation based on theformula:

Circularity=(4πS)^(1/2) /L,

where π represents the circular constant, S represents the area of theprojected figure, and L represents the circumference of the projectedfigure was used as the average circularity of the particles. The averagecircularity was also obtained by analyzing arbitrarily selected 50particles in an electron microscopic image (100×) of the particles usingan image analysis program Mac-View available from Mountech Co., Ltd.based on the formula:

Circularity=(4πS)^(1/2) /L,

where π represents the circular constant, S represents the area of theprojected figure, and L represents the circumference of the projectedfigure. The obtained average circularity was almost the same as thatobtained using FPIA-2100.

Measurement of Film Thickness

In the application of the compositions to form a laminate of coatingfilms described later, the respective compositions were simultaneouslyapplied to a dummy aluminum plate (A-1050P). The thicknesses of therespective coating films formed on the dummy aluminum plate weremeasured with an eddy-current film thickness meter available from SankoElectronic Laboratory Co., Ltd., and treated as the thicknesses of therespective layers.

Abrasion Resistance

A pad for industrial use (trade name: Scotch-Brite 7447C) available from3M Company was cut into a size of 3 cm square, and a 2 cc portion of a5% neutral detergent was dropped thereon. The obtained pad wasreciprocated on the film at a load of 4.5 kg, and the abrasionresistance was evaluated by the number of reciprocating motions untilthe substrate was exposed.

Preparation of Top-Coat Coating Composition

To an aqueous coating composition containing a fluororesin as a maincomponent was added a predetermined amount of inorganic particles, andstirred and mixed to prepare a top-coat coating composition.

Examples 1 to 3 and 6 to 24, Comparative Examples 1 to 4

The following components were mixed and then blended with apredetermined amount of predetermined inorganic particles as specifiedin Table 1. The mixture was stirred to prepare a top-coat coatingcomposition.

Tetrafluoroethylene polymer aqueous dispersion (solid content of 62%):66.7 parts

Film forming agent: 12.4 parts

Carbon black millbase (solid content of 20%): 0.5 parts

Pearl luster pigment: 0.8 parts

Surfactant: 5.6 parts

Water: 14.0 parts

In Examples 16 and 17 and Comparative Example 4, “substantiallyspherical” silicon carbide (average particle size: 17 μm, averagecircularity: 0.97) described later and “non-spherical” silicon carbide(average particle size: μm, average circularity: 0.86) were uniformlymixed at a ratio of 83:17, 50:50, and 10:90, respectively, and used Eachmixture had an average circularity as shown An Table 1.

Example 4

The following components were mixed and then blended with apredetermined amount of predetermined inorganic particles as specifiedin Table 1. The mixture was stirred to prepare a top-coat coatingcomposition.

Tetrafluoroethylene polymer aqueous dispersion (solid content of 62%):33.3 parts

Tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer aqueousdispersion (solid content of 62%): 33.4 parts

Film forming agent: 12.4 parts

Carbon black millbase (solid content of 20%): 0.5 parts

Pearl luster pigment: 0.8 parts

Surfactant: 5.6 parts

Water: 14.0 parts

Example 5

The following components were mixed and then blended with apredetermined amount of predetermined inorganic particles as specifiedin Table 1. The mixture was stirred to prepare a top-coat coatingcomposition.

Tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer aqueousdispersion (solid content of 62%): 66.7 parts

Film forming agent: 12.4 parts

Carbon black millbase (solid content of 20%): 0.5 parts

Pearl luster pigment: 0.8 parts

Surfactant: 5.6 parts

Water: 14.0 parts

Example 25

The following components were mixed and then blended with apredetermined amount of predetermined inorganic particles as specifiedin Table 1. The mixture was stirred to prepare a top-coat coatingcomposition.

Tetrafluoroethylene polymer aqueous dispersion (solid content of 62%):13.3 parts

Tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer aqueousdispersion (solid content of 62%): 53.4 parts

Film forming agent: 12.4 parts

Carbon black millbase (solid content of 20%): 0.5 parts

Pearl luster pigment: 0.8 parts

Surfactant: 5.6 parts

Water: 14.0 parts

Coating compositions a to e shown in Table 1 had the followingcompositions.

Coating Composition a

Tetrafluoroethylene polymer aqueous dispersion (solid content of 62%):65.6 parts

Film forming agent: 12.2 parts, Carbon black millbase (solid content of20%): 0.5 parts

Pearl luster pigment: 0.8 parts

Silicon carbide (average particle size of 17 μm, average circularity of0.97): 1.8 parts

Surfactant: 5.5 parts

Water: 13.6 parts

Coating Composition b

Tetrafluoroethylene polymer aqueous dispersion (solid content of 62%):66.7 parts

Film forming agent: 12.4 parts

Carbon black millbase (solid content of 20%): 0.5 parts

Pearl luster pigment: 0.8 parts

Surfactant: 5.6 parts

Water: 14.0 parts

Coating Composition c

Tetrafluoroethylene polymer aqueous dispersion (solid content of 62%):32.0 parts

Carbon black millbase (solid content of 25%): 8.4 parts

PES aqueous dispersion. (solid content of 20%): 24.3 parts

Silicon carbide (average particle size of 17 μm, average circularity of0.97): 1.8 parts

Surfactant: 2.0 parts

Thickener: 14.2 parts

Water: 17.3 parts

Coating Composition d

Tetrafluoroethylene polymer aqueous dispersion (solid content of 62%):32.4 parts

Carbon black millbase (solid content of 25%): 8.6 parts

PES aqueous dispersion (solid content of 20%): 24.8 parts

Surfactant: 2.0 parts

Thickener: 14.4 parts

Water: 17.8 parts

Coating Composition e

Carbon black millbase (solid content of 20%): 1.4 parts PES aqueousdispersion (solid content of 20%): 50.3 parts

Thickener: 10.7 parts

Silicon carbide (average particle size of 12 μm, average circularity of0.86): 18.7 parts

Surfactant: 3.0 parts

Water: 15.9 parts

Examples 1 to 5, 8 to 17, and 25, Comparative Examples 1 to 4Preparation of Test Plate

A surface of an aluminum plate (A-10502) was degreased with acetone, andthen roughened by sand-blasting so as to have a surface roughness Ra of2.0 to 3.0 μm determined in conformity with JIS B0601-2001. Costs on thesurface were removed by air blowing. The coating composition shown inTable 1, as a primer, was spray-applied using a gravity-feed spray gunat a spraying pressure of 0.2 MPa so as to have a dry thickness of 10 to15 μm. The resulting coating film on the aluminum plate was dried at 80°C. to 100° C. for 15 minutes, and then cooled down to room temperature.To the obtained primer coating film was spray-applied the top-coatcoating composition shown in Table 1 to have a thickness after firing asspecified in Table 1. The resulting coated plate was dried at 80° C. to100° C. for 15 minutes and then fired at 380° C. for 20 minutes toprepare a test coated plate. The obtained test coated plate was alaminate in which the primer layer and a top coat shown in Table 1 wereformed on an aluminum plate.

Examples 6, 7, 18, and 19 Preparation of Test Plate

A surface of an aluminum plate (A-1050P) was degreased with acetone, andthen roughened by sand-blasting so as to have a surface roughness Ra of2.0 to 3.0 μm determined in conformity with JIS B0601-2001. Dusts on thesurface were removed by air blowing. The coating composition shown inTable 1, as a primer, was spray-applied using a gravity-feed spray gunat a spraying pressure of 0.2 MPa so as to nave a dry thickness of 10 to15 μm. The resulting coating film on the aluminum plate was dried at 80°C. to 100° C. for 15 minutes, and then cooled down to room temperature.Next, the coating composition shown in Table 1 as the coatingcomposition for an intermediate layer 1 was applied to a dry thicknessof 10 to 20 μm. The resulting coating film on the aluminum plate wasdried at 80° C. to 100° C. for 15 minutes, and then cooled down to roomtemperature. To the obtained coating film was spray-applied the top-coatcoating composition shown in Table 1 to have a thickness after firing asspecified in Table 1.

The resulting coated plate was dried at 80° C. to 100° C. for 15 minutesand then fired at 380° C. for 20 minutes to prepare a test coated plate.The obtained test coated plate was a laminate in which the primer layer,the intermediate layer 1, and a top coat shown in Table 1 were formed onthe aluminum plate.

Examples 20 to 24

A surface of an aluminum plate (A-10502) was degreased with acetone, andthen roughened by sand-blasting so as to have a surface roughness Ra of2.0 to 3.0 μm determined in conformity with JIS B0601-2001. Dusts on thesurface were removed by air blowing. The coating composition shown inTable 1, as a primer, was spray-applied using a gravity-feed spray gunat a spraying pressure of 0.2 MPa so as to have a dry thickness of 10 to15 μm. The resulting coating film on the aluminum plate was dried at 80°C. to 100° C. for 15 minutes, and then cooled down to room temperature.Next, the coating composition shown in Table 1 as the coatingcomposition for an intermediate layer 2 was applied to a dry thicknessof 10 to 20 μm. The resulting coating film on the aluminum plate wasdried at 80° C. to 100° C. for 15 minutes, and then cooled down to roomtemperature.

Next, the coating composition shown in Table 1 as the coatingcomposition for an intermediate layer 1 was applied to a dry thicknessof 10 to 20 μm. The resulting coating film on the aluminum plate wasdried at 80° C. to 100° C. for 15 minutes, and then cooled down to roomtemperature. To the obtained coating film was spray-applied the top-coatcoating composition shown in Table 1 to have a thickness after firing asspecified in Table 1. The resulting coated plate was dried at 80° C. to100° C. for 15 minutes and then fired at 380° C. for 20 minutes toprepare a test coated plate. The obtained test coated plate was alaminate in which the primer layer, intermediate layer 2, intermediatelayer 1, and a top coat shown in Table 1 were formed on the aluminumplate. Table 1 shows the results of the abrasion resistance test.

The inorganic particles used were commercially available particles ofalumina, silicon carbide, or glass beads. Inorganic particles preparedby pulverization to be used as an abrasive were used as “non-sphericalinorganic particles”, and inorganic particles treated by a knownspraying spheroidization or the like were used as “substantiallyspherical inorganic particles”. Table 1 shows the average particle sizeand average circularity of the particles.

It should be noted that alumina has a new Mohs hardness of 12, siliconcarbide has a new Mohs hardness of 14, and glass beads have a new Mohshardness of 7. Moreover, it is known that a pearl luster pigment in thecoating composition has a new Mobs hardness corresponding to 3 andcarbon black has a new Mobs hardness of 1 to 3.

Example 1 in which spherical alumina particles were used achievedmarkedly higher abrasion resistance than Comparative Example 1 in whichnon-spherical alumina was used in the same amount.

Example 2 in which spherical particles of silicon carbide that has astill higher hardness than alumina achieved excellently high abrasionresistance which was much higher than that achieved in ComparativeExample 2 in which non-spherical silicon carbide was used in the sameamount. Comparative Example 3 in which spherical glass beads in the sameamount were used failed to achieve sufficient abrasion resistance.

Example 3 in which a larger amount of spherical silicon carbide was usedachieved still higher abrasion resistance.

in Example 4, the fluororesin used was a mixture of equal parts of PTFEand PFA. In Example 5, the fluororesin used was PFA alone. In comparisonof these examples with Example 2 in which the fluororesin used was PTFEalone, Example 2 achieved the highest abrasion resistance.

In Example 6, the same top-coat coating composition. as that used inExample 2, the coating composition d for the intermediate layer 1, andthe coating composition e as a primer were applied to form triplecoating, resulting in still higher abrasion resistance.

In Example 7, the same top-coat coating composition as that used inExample 3, the coating composition d for the intermediate layer 1, andthe coating composition e as a primer were applied to form triplecoating, resulting in extremely high abrasion resistance.

In Example 8, though the amount of spherical silicon carbide was reducedto half of that in Example 2, the abrasion resistance was sufficientlyhigh in comparison with that in Comparative Example 2.

In Example 9, the amount of spherical silicon carbide was furtherincreased compared to that in Example 3 to improve the abrasionresistance. However, the degree of the improvement was small.

In Example 10, the top-coat coating composition was applied to a smallerthickness than that in Example 2, resulting in still sufficiently highabrasion resistance.

In Example 11, the thickness of the top-coat coating composition wasincreased, resulting in a remarkable improvement of the abrasionresistance.

In Examples 12 to 14, the abrasion resistance was better as thespherical silicon carbide had a larger average particle size. Example 15in which spherical silicon carbide having a large average particle sizewere used and the coating film formed was thick achieved still higherabrasion resistance.

In Examples 16 and 17 and Comparative Example 4, spherical siliconcarbide (average particle size: 17 μm, average circularity: 0.97) andnon-spherical silicon carbide (average particle size: 17 μm, averagecircularity: 0.86) were uniformly mixed at a ratio of 83:17, 50:50, and10:90, respectively, and used. The average circularity after the mixingand the abrasion resistance of the coating film were as shown in Table1.

In Examples 18 and 19, the top--coat coating composition was prepared inthe same manner as in Example 2, except that no binder resin was used.The resulting composition was used for an intermediate layer, and triplecoating was formed. In each example, high abrasion resistance wasachieved.

In Examples 20 to 24, various configurations of coating films wereemployed and quadruple coating was formed, resulting in extremely highabrasion resistance in each example.

Example 25 in which a mixture of PTFE and PFA at a mass ratio of 20:80was used as a fluororesin achieved. higher abrasion resistance thanExample 5.

The coating film of Example 2 was cut into a size of 3 cm square andheated to 600° C. or higher at which the fluororesin is burned off. Byelemental mapping of the residues using SEM-EDX, a part corresponding tothe silicon carbide was specified. The average circularity ofarbitrarily selected 50 silicon carbide particles in the image wasmeasured using an image analysis program Mac-View available fromMountech Co., Ltd. based on the formula:

Circularity=(4πS)^(1/2) /L,

where π represents the circular constant, S represents the area of theprojected figure, and L represents the circumference of the projectedfigure. The obtained value was 0.98 which was almost the same as thatmeasured before application of the coating composition.

Moreover, the values of the average circularity of the silicon carbidein the residues of the coating films of Examples 16 and 17 andComparative Example 2 were determined in the same manner as in the caseof the coating film of Example 2, and were 0.93, 0.92, and 0.88,respectively, which were almost the same as those measured beforeapplication of the coating composition.

TABLE 1 Top coat Top-coat coating composition Inorganic particlesAverage Amount Amount particle relative to relative to New Mohs sizeAverage fluororesin fluororesin Thickness Fluororesin Material hardness(μm) circularity (wt %) (vol %) (μm) Example 1 PTFE Alumina 12 17 0.98 42 20 Example 2 PTFE Silicon carbide 14 17 0.97 4 3 20 Example 3 PTFESilicon carbide 14 17 0.97 10 7 20 Example 4 PTFF/PFA = Silicon carbide14 17 0.97 4 3 20 50/50 Example 5 PFA Silicon carbide 14 17 0.97 4 3 20Example 6 PTFE Silicon carbide 14 17 0.97 4 3 20 Example 7 PTFE Siliconcarbide 14 17 0.97 10 7 20 Example 8 PTFE Silicon carbide 14 17 0.97 2 120 Example 9 PTFE Silicon carbide 14 17 0.97 20 13 20 Example 10 PTFESilicon carbide 14 17 0.97 4 3 15 Example 11 PTFE Silicon carbide 14 170.97 4 3 30 Example 12 PTFE Silicon carbide 14 19 0.98 4 3 20 Example 13PTFE Silicon carbide 14 26 0.97 4 3 20 Example 14 PTFE Silicon carbide14 34 0.96 4 3 20 Example 15 PTFE Silicon carbide 11 34 0.96 4 3 30Example 16 PTFE Silicon carbide 14 17 0.94 4 3 20 Example 17 PTFESilicon carbide 14 17 0.92 4 3 20 Example 18 PTFE Silicon carbide 14 170.97 4 3 20 Example 19 PTFE Silicon carbide 14 17 0.97 4 3 20 Example 20PTFE Silicon carbide 14 17 0.97 4 3 20 Example 21 PTFE Silicon carbide14 17 0.97 4 3 20 Example 22 PTFE Silicon carbide 14 17 0.97 4 3 20Example 23 PTFE Silicon carbide 14 17 0.97 4 3 20 Example 24 PTFESilicon carbide 14 17 0.97 4 3 20 Example 25 PTFE/PFA = Silicon carbide14 17 0.97 4 3 20 20/80 Comparative PTFE Alumina 12 17 0.86 4 2 20Example 1 Comparative PTFE Silicon carbide 14 21 0.87 4 3 20 Example 2Comparative PTFE Glass 7 15 0.98 4 4 20 Example 3 Comparative PTFESilicon carbide 14 17 0.88 4 3 20 Example 4 Intermediate layer 1Intermediate layer 2 Primer layer Abrasion Coating Thickness CoatingThickness Coating Thickness resistance composition (μm) composition (μm)composition (μm) (times) Example 1 — — — — d 10 2000 Example 2 — — — — d10 20500 Example 3 — — — — d 10 47000 Example 4 — — — — d 10 8000Example 5 — — — — d 10 4500 Example 6 d 15 — — e 10 22500 Example 7 d 15— — e 10 53000 Example 8 — — — — d 10 11000 Example 9 — — — — d 10 48000Example 10 — — — — d 10 10000 Example 11 — — — — d 10 32000 Example 12 —— — — d 10 21000 Example 13 — — — — d 10 38000 Example 14 — — — — d 1040000 Example 15 — — — — d 10 50000 Example 16 — — — — d 10 18000Example 17 — — — — d 10 8000 Example 18 a 15 — — d 10 53500 Example 19 b15 — — d 10 22500 Example 20 a 15 d 15 e 10 55000 Example 21 b 15 d 15 e10 24500 Example 22 d 15 d 15 e 10 25000 Example 23 b 15 c 15 d 10 28000Example 24 a 15 c 15 e 10 72500 Example 25 — — — — d 10 6500 Comparative— — — — d 10 500 Example 1 Comparative — — — — d 10 2000 Example 2Comparative — — — — d 10 <100 Example 3 Comparative — — — — d 10 3000Example 4

1. A coating composition comprising: a fluororesin; and inorganicparticles, the inorganic particles having a new Mohs hardness of 10 orhigher and having a substantially spherical shape.
 2. The coatingcomposition according to claim 1, wherein the inorganic particles viewedfrom an arbitrary angle have an average circularity of 0.90 to 1.00. 3.The coating composition according to claim 1, wherein the inorganicparticles are at least one kind selected from the group consisting ofalumina particles and silicon carbide particles.
 4. The coatingcomposition according to claim 1, wherein the fluororesin ispolytetrafluoroethylene.
 5. The coating composition according to claim1, wherein the fluororesin contained includes polytetrafluoroethylenealone or polytetrafluoroethylene and a fluororesin other thanpolytetrafluoroethylene, and the amount of the polytetrafluoroethyleneis 20% by mass or more relative to the total amount of thepolytetrafluoroethylene and the fluororesin other thanpolytetrafluoroethylene.
 6. The coating composition according to claim1, wherein the amount of the inorganic particles is 1 to 40% by massrelative to the amount of the fluororesin.
 7. A coating film producedfrom the coating composition according to claim
 1. 8. A coating filmcomprising: a fluororesin; and inorganic particles, the inorganicparticles having a new Mohs hardness of 10 or higher and having asubstantially spherical shape.
 9. The coating film according to claim 8,wherein the inorganic particles viewed from an arbitrary angle have anaverage circularity of 0.90 to 1.00.
 10. The coating film according toclaim 8, wherein the inorganic particles are at least one kind selectedfrom the group consisting of alumina particles and silicon carbideparticles.
 11. The coating film according to claim 8, wherein thefluororesin is polytetrafluoroethylene.
 12. The coating film accordingto claim 8, wherein the fluororesin contained includespolytetrafluoroethylene alone or polytetrafluoroethylene and afluororesin other than polytetrafluoroethylene, and the amount of thepolytetrafluoroethylene is 20% by mass or more relative to the totalamount of the polytetrafluoroethylene and the fluororesin other thanpolytetrafluoroethylene.
 13. The coating film according to claim 8,wherein the amount of the inorganic particles is 1 to 40% by massrelative to the amount of the fluororesin.
 14. A laminate comprising: asubstrate; and a coating film produced from the coating compositionaccording to claim
 1. 15. The laminate according to claim 14, which is acooking utensil.